This invention relates in general to transceiver apparatus and more particularly, to an improved coherent modulated optical sensor adaptable for use within a missile or bomb fuze, and wherein a comparison between sub-carrier and baseband detection channels may be employed for determining whether a target is real or an aerosol, thereby preventing the optical sensor from prefunctioning due to the aerosol.
Optical sensors of the type which are adapted for inclusion within a tracking system are well known in the art. However, prior art optical sensors do not modulate the intensity of the optical energy generated thereby. Hence, these systems measure only the range of a target by video detecting the return pulses from the target. Furthermore, these systems cannot readily discriminate against pulses which might be returned from an aerosol and pulses which might be returned from a dull target. Therefore, in some prior art optical sensors, a threshold signal might be obtained from an aerosol which could cause the missile or bomb fuze to prefunction.
Conventional radio frequency (RF) Doppler radar systems suffer from the disadvantage of being readily susceptible to electronic counter measures. However, because the field of view of the optical sensor of the invention is much narrower than that of conventional RF radar systems, electronic counter measure against such a system is much more difficult.
Accordingly, it is an object of the present invention to provide an improved optical sensor in which target velocity information can be obtained from a predetermined target having relative motion thereto.
Another object of the present invention is to provide an improved optical sensor for use in a missile or free fall munition fuze system which has aerosol rejection capabilities.
Still another object of the present invention is to provide an improved optical sensor for use within a missile or bomb fuze system wherein the optical energy transmitted is a series of pulses which are intensity modulated by a radio frequency sub-carrier signal.
Yet another object of the present invention is to provide an improved coherent modulated sensor of the foregoing type wherein the received pulses are phase coherent with the transmitted pulses.
A further object of the present invention is to provide an improved coherent modulated sensor of the foregoing type wherein the transmitting of pulses of intensity modulated optical energy and the down converting of the received pulse information is effected by a radio frequency reference signal.
A still further object of the present invention is to provide an improved coherent modulated sensor of the foregoing type wherein the receiver portion thereof includes a radio frequency sub-carrier channel and a baseband channel for comparison of the magnitude of the Doppler signal to the average direct current power comprising the received pulses to provide for aerosol rejection.